1. Field of the Invention
The present invention relates to a fluid control system including a vacuum chamber, a gas supply source to supply gas which is a fluid to the vacuum chamber, an exhaust pipe to discharge the fluid from the vacuum chamber, a gas supply pipe connecting the gas supply source to the vacuum chamber, and a pressure sensor to detect the internal pressure of the vacuum chamber.
2. Related Art
As a fluid control system having been conventionally used, there is a vacuum control system 100 shown in FIG. 7, for example. This vacuum control system 100 includes a vacuum chamber 101 for performing a film deposition process on a semiconductor wafer. In the vacuum chamber 101, one wafer or a plurality of wafers are to be disposed. The vacuum chamber 101 is connected to a vacuum pump 104 serving as a vacuum source through an exhaust pipe 102 via a metering valve 103. The vacuum chamber 101 is also connected to a gas supply source 108 through a gas supply pipe 105 via a shut-off valve 106 and a mass flow controller 107 for controlling a flow rate of a fluid. To the exhaust pipe 102, a vacuum pressure sensor 109 and the metering valve 103 are attached. The sensor 109 and the metering valve 103 are connected to a controller 110 for controlling an opening degree of the metering valve 103 based on a pressure value measured by the sensor 109.
Operations of the conventional vacuum control system 100 having the above configuration will be explained below referring to FIG. 8, which is a time chart showing the operations of the vacuum control system 100. In FIG. 8, a horizontal axis of graphs (a) to (d) represents time, a vertical axis of the graph (a) represents a pressure and a solid line P2 indicates the internal pressure of the vacuum chamber 101, a vertical axis of the graph (b) represents a flow rate and a solid line M2 indicates the flow rate of a process gas passing through the mass flow controller 107, a vertical axis of the graph (c) represents an opening degree and a solid line H2 indicates the opening degree of the shut-off valve 106, and a vertical axis of the graph (d) represents an opening degree and a solid line V2 indicates the opening degree of the metering valve 103.
The vacuum control system 100 is arranged to provide a stage TA2 in which the internal pressure of the vacuum chamber 101 is at a vacuum state value R and a stage TC2 in which the internal pressure of the vacuum chamber 101 is at a pressure set value Q. Furthermore, the system 100 further provides a stage TB2 to adjust the internal pressure to the pressure set value Q and a stage TD2 to adjust the internal pressure to the vacuum state value R. In other words, the vacuum control system 100 is configured to repeat a cycle from the stage TA2 via the stage TB2 and the stage TC2 to the stage TD2, and back to the stage TA2, to deposit a film on each wafer.
In the stage TA2, the shut-off valve 106 is closed and the metering valve 103 is opened. Thus, the vacuum pressure in the vacuum chamber 101 is brought into a vacuum state value R (a fully evacuated state) by the vacuum pump 104.
In the stage TB2, in order to control or adjust the internal pressure of the vacuum chamber 101 from the vacuum state value R to the pressure set value Q, the metering valve 103 is turned to a closed state in a short time as shown by the solid line V2 while the shut-off valve 106 is turned to an open state indicated by the solid line H2. When the shut-off valve 106 is opened, the process gas at a flow rate controlled by the mass flow controller 107 as indicated by the solid line M2 is allowed to flow at a constant rate. When a constant rate of the process gas flows in the vacuum chamber 101, the pressure inside the vacuum chamber 101 rises as indicated by the solid line P2.
In the stage TC2, the vacuum pressure sensor 109 measures that the internal pressure of the vacuum chamber 101 reaches the pressure set value Q.
At the same time when the internal pressure reaches the pressure set value Q, the metering valve 103 is opened as indicated by the solid line V2. Accordingly, the internal pressure of the vacuum chamber 101 is made stable at the pressure set value Q as shown by the solid line P2.